J/A+A/622/A99ivo://CDS.VizieR/J/A+A/622/A99doi:10.26093/cds/vizier.36220099CDSLouvet F.Neupane S.Garay G.Russeil D.Zavagno A.Gomez L.,Guzman A.Bronfman L.Nony T.2019-02-27T14:17:11Z2019-02-07T09:07:02ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmolecular-cloudsspectroscopyThe formation of high-mass stars remains unknown in many aspects. Two families of models compete to explain the formation of high-mass stars. On the one hand, quasi-static models predict the existence of high-mass pre-stellar cores sustained by a high degree of turbulence. On the other hand competitive accretion models predict that high-mass proto-stellar cores evolve from low/intermediate mass proto-stellar cores in dynamic environments. The aim of the present work is to bring observational constraints at the scale of high-mass cores (~0.03pc). We targeted with ALMA and MOPRA a sample of 9 starless massive dense cores (MDCs) discovered in a recent Herschel/HOBYS study. Their mass and size (~110M_{sun}_ and r=0.1pc, respectively) are similar to the initial conditions used in the quasi-static family of models explaining for the formation of high-mass stars.We present ALMA 1.4mm continuum observations that resolve the Jeans length ({lambda}_Jeans_~0.03pc) and that are sensitive to the Jeans mass (M_Jeans_~0.65M_{sun}_) in the 9 starless MDCs, together with ALMA-^12^CO(2-1) emission line observations. We also present HCO^+^(1-0), H^13^CO+(1-0) and N_2_H^+^(1-0) molecular lines from the MOPRA telescope for 8 of the 9 MDCs. The 9 starless MDCs have the mass reservoir to form high-mass stars according to the criteria by Baldeschi et al. (2017MNRAS.466.3682B). Three of the starless MDCs are subvirialized with {alpha}_vir_~0.35, and 4 MDCs show sign of collapse from their molecular emission lines. ALMA observations show very little fragmentation within the MDCs. Only two of the starless MDCs host compact continuum sources, whose fluxes correspond to <3M_{sun}_ fragments. Therefore the mass reservoir of the MDCs has not yet been accreted onto compact objects, and most of the emission is filtered out by the interferometer. These observations do not support the quasi-static models for high-mass star formation since no high-mass pre-stellar core is found in NGC6334. The competitive accretion models, on the other hand, predict a level of fragmentation much higher than what we observe2019A&A...622A..99Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/622/A99CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/602/A77 : HOBYS: 46 MDCs found in NGC 6334 (Tige+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/622/A99https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/622/A99http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/622/A99https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/622/A99https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/622/A99http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/622/A99GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/622/A99/table2 (Physical parameters of the fragments)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/622/A99/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/622/A99/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/622/A99/table2?GETtext/xml+votable180.050000true259.771875-36.13068890.005555555555555556Cone search capability for table J/A+A/622/A99/tablea1 (Additional parameters of the MDCs)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/622/A99/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/622/A99/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/622/A99/tablea1?GETtext/xml+votable180.050000true260.009-36.20402780.005555555555555556Cone search capability for table J/A+A/622/A99/list (List of fits spctra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/622/A99/list?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/622/A99/list?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/622/A99/list?GETtext/xml+votable180.050000true260.009-36.20402780.0055555555555555566/42456-42458https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/622/A99?format=asciidefaultJ/A+A/622/A99/table1Physical parameters of the MDCsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMDCMDC name (NGC6334-MDC NN)meta.id;meta.maincharRadRadius (Mean value 0.090)pcphys.size.radiusfloatMassMass (Mean value 116)solMassphys.massintvN2H+? N_2_H^+^ velocitykm/sspect.dopplerVelocfloatnullablesigmaN2H+? N_2_H^+^ velocity dispersion (Mean value 1.12)km/sphys.veloc.dispersionfloatnullablevHCO+? HCO^+^ velocitykm/sspect.dopplerVelocfloatnullablevH13CO+? H^13^CO^+^ velocitykm/sspect.dopplerVelocfloatnullabledeltaV? Asymmetry parameter, {delta}V=(V_thick_-V_thin_))/{sigma}V_thin_) (1)src.morph.paramfloatnullableMvir? Virial mass (Mean value 71)solMassphys.massintnullablealphavir? Virial parameter alpha (Mean value 0.60)phys.mass;arith.ratiofloatnullableMthrThreshold mass (Mean value 40.0)solMassphys.massfloatMJeansJeans mass (Mean value 0.64)solMassphys.massfloatlambdaJeansJeans scale, {lambda}_Jeans_ (Mean value 32)pctime.scaleintBfield? Magnetic field (Mean value 1.2)mGphys.magFieldfloatnullableP17Display the Tige et al. data (2017, Cat. J/A+A/602/A77)meta.ref.urlcharJ/A+A/622/A99/table2Physical parameters of the fragmentsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSourceSource name (1)meta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainFluxIntegrated flux (Mean value 9.0+/-0.4)mJyphot.flux.density;em.radiofloate_Fluxrms uncertainty on FluxmJystat.error;phot.fluxfloatSize1Size (Mean value 1.0x0.8)arcsecphys.angSizefloatSize2Size (Mean value 1.0x0.8)arcsecphys.angSizefloatMassMass (method to derive the mass follows eq. (2)) (Mean value 0.90+/-0.03)solMassphys.mass;stat.meanfloate_Massrms uncertainty on MasssolMassstat.error;phys.massfloatJ/A+A/622/A99/tablea1Additional parameters of the MDCsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMDCSource name, NGC6334-MDC NN (1)meta.id;meta.maincharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainLbolBolometric luminosity (Meand value 203) (1)solLumphys.luminosityintM/LMass to light ratiosolMass/solLumphys.composition.massLightRatiofloat<nH2>Mean H_2_ density number (Mean value 2.0E+6) (1)cm**-3meta.number;phys.density;stat.meandoubleTTemperature (Mean value 15.5) (1)Kphys.temperaturefloatsigma12CO^1^CO velocity dispersion (Mean value 16.6) (2)mJy/beamphys.veloc.dispersionfloatsigmacontContinuum velocity dispersion (Mean value 336) (3)uJy/beamphys.veloc.dispersionintMassSenMass sensitivity at 5{sigma} (Mean value 0.11) (4)solMassphys.massfloatJ/A+A/622/A99/tablea2Integration parameters of the CO line in the MDCsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMDCMDC namemeta.id;meta.maincharbVelBSLower value of blue-shifted ^12^CO(2-1) emission velocity rangekm/sspect.dopplerVelocfloatBVelBSUpper value of blue-shifted ^12^CO(2-1) emission velocity rangekm/sspect.dopplerVelocfloatsigmaB1{sigma} value for blue-shifted ^12^CO(2-1)stat.errorfloatbVelRSLower value of red-shifted ^12^CO(2-1) emission velocity rangekm/sspect.dopplerVelocfloatBVelRSUpper value of red-shifted ^12^CO(2-1) emission velocity rangekm/sspect.dopplerVelocfloatsigmaR1{sigma} value for red-shifted ^12^CO(2-1)stat.errorfloatJ/A+A/622/A99/listList of fits spctraspShow the spectrummeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainNxNumber of pixels along X-axismeta.numberintObs.dateObservation date (YYYY-MM-DDThh:mm:ss.sss"stime.epoch;obsnullablebFreqLower value of relative frequency intervalHzem.freq;stat.mindoubleBFreqUpper value of relative frequency intervalHzem.freq;stat.maxdoubledFreqFrequency resolutionHzspect.resolutionfloatsizeSize of FITS fileKibytephys.size;meta.fitsintFileNameName of FITS file, in subdirectory fitsmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fits